Analog Devices Inc. LTC3803ES6-3#TRPBF

Overview

LTC3803ES6-3#TRPBF from Analog Devices (formerly Linear Technology) is a constant-frequency current-mode flyback DC/DC controller in a 6-lead ThinSOT™ package, optimized for driving N-channel MOSFETs in high-input-voltage telecom and automotive housekeeping supplies. It delivers ±1.5% output voltage accuracy, 300 kHz fixed switching frequency, 240 μA quiescent current, and operates across –40°C to 125°C. Used in nonisolated 5 V/2 A telecom power supplies with 36–72 V input.

For engineers reviewing the LTC3803ES6-3#TRPBF datasheet, LTC3803ES6-3#TRPBF pinout, LTC3803ES6-3#TRPBF application, or LTC3803ES6-3#TRPBF equivalent, key selection criteria include its ground-referenced current sensing architecture, programmable slope compensation via external resistor, internal soft-start (1.4 ms), micropower hysteretic start-up, and VCC shunt regulation enabling direct high-VIN biasing without auxiliary winding.

Technical Context

The LTC3803ES6-3#TRPBF implements a current-mode control loop where the ITH/RUN pin voltage sets the current comparator threshold, directly modulating peak switch current in proportion to output load deviation. Its 300 kHz oscillator drives an RS latch that controls NGATE turn-on timing, while blanking and slope compensation prevent subharmonic oscillation at duty cycles above 50%.

Startup relies on dual mechanisms: a wide-hysteresis UVLO (VTURNON = 8.7 V, VTURNOFF = 5.7 V) and ITH/RUN forced shutdown (VITHSHDN = 0.28 V). The internal VCC shunt regulator clamps at ~9.5 V and draws up to 25 mA, allowing direct high-VIN powering through a single resistor-eliminating need for transformer bias windings in simpler designs.

Key Specifications

Pinout & Package

The LTC3803ES6-3#TRPBF is housed in a low-profile (1 mm height) 6-lead TSOT-23 (ThinSOT™) package, compatible with standard SOT-23 reflow profiles and space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar flyback controller applications.

Compared with UCC28C43DR and MAX17595ATP+T, the LTC3803ES6-3#TRPBF uniquely combines ultra-low quiescent current (240 μA), internal VCC shunt regulation for single-resistor start-up, and guaranteed ±1.5% reference accuracy across –40°C to 125°C - making it optimal for space- and efficiency-constrained telecom and automotive auxiliary supplies.

Availability

LTC3803ES6-3#TRPBF is available at Aetrix Electronics and suitable for telecom housekeeping supplies, automotive auxiliary power, Power over Ethernet powered devices, and industrial control auxiliary rails requiring stable component supply with extended temperature support and long lifecycle assurance.

Supply support for LTC3803ES6-3#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains its high-performance power management portfolio with rigorous automotive and industrial qualification standards.

The LTC3803 series was designed specifically for high-input-voltage flyback and boost converters in space-constrained, efficiency-critical applications such as telecom infrastructure and automotive subsystems.

FAQ

What is the maximum input voltage the LTC3803ES6-3#TRPBF can handle?

The LTC3803ES6-3#TRPBF itself has an absolute maximum VCC rating of 8 V from a low-impedance source, but its internal shunt regulator allows it to be powered directly from inputs up to 72 V via a series resistor. External components-not the IC-determine practical VIN limits; the datasheet shows operation from 36 V to 72 V in telecom applications, with MOSFET and transformer ratings governing upper bound.

Does the LTC3803ES6-3#TRPBF require an optocoupler for feedback?

No, the LTC3803ES6-3#TRPBF supports primary-side regulation using only a resistive divider on the output, eliminating the need for an optocoupler or secondary-side TL431. Its precise 0.8 V reference and ±1.5% accuracy enable stable regulation without isolation components-reducing cost, size, and failure points in nonisolated or transformer-coupled flyback designs.

How does the LTC3803ES6-3#TRPBF achieve stable operation at high duty cycles?

The LTC3803ES6-3#TRPBF injects a linear 5 μA ramp current from the SENSE pin into an external resistor (RSL) to provide programmable slope compensation. This ramp adds a duty-cycle-dependent voltage to the current sense signal, preventing subharmonic oscillation above 50% duty cycle. A typical 5.9 kΩ RSL yields 30 mV compensation at 80% duty, stabilizing the current-mode loop without requiring complex compensation networks.

Can the LTC3803ES6-3#TRPBF operate without a transformer bias winding?

Yes-the LTC3803ES6-3#TRPBF's internal VCC shunt regulator enables direct high-VIN powering through a single resistor and bypass capacitor (e.g., 72 V → 100 kΩ → VCC → 1 μF). This eliminates dependency on a third transformer winding, simplifying layout and reducing bill-of-materials for cost-sensitive or space-constrained designs where efficiency trade-offs are acceptable.

What is the purpose of the ITH/RUN pin on the LTC3803ES6-3#TRPBF?

The ITH/RUN pin on the LTC3803ES6-3#TRPBF serves two critical functions: it acts as the error amplifier output node-setting the current comparator threshold-and as the run/shutdown control input. Pulling it below 0.28 V forces shutdown; during normal operation, its voltage (0.7–1.9 V) directly commands peak switch current. It also serves as the compensation point for the voltage loop when an RC network is connected to ground.